The harnesses for single shaft horse-drawn vehicles have existed since ancient times: even the Sumerians (about 3000 BC) used the principle of a single dorsal shaft on their chariots, the shaft being attached to the horse by a neck collar. But this type of harness required distributing the forces among several horses harnessed in front.
This technique was totally abandoned by the beginning of the 20th century, when several new arrangements were proposed:
first there was proposed a harness articulated to a small saddle about a vertical axis of articulation, the small saddle being mounted on the horse by a shoulder collar. This device was more particularly intended for agricultural use and the pivotal articulation permitted easily maneuvering at the end of the field. However it only permitted movement in the direction of the furrow. PA0 another device described in U.S. Pat. No. 3,847,408: the shaft is mounted on a small saddle in a semi-rigid fashion which permits avoiding veering during trotting. The small saddle is strapped in a conventional manner by means of belly bands and maintained in longitudinal position by a collar of the hunting collar type and a thong which passes about the forehead of the horse, which prevents rearward displacement. However, this harness does not permit sharp turns and can be used only on flat straightaways or very wide curves. Moreover, the collar and the forehead thong do not assure the desired position and rapidly become excessively tightened which considerably troubles the animal. PA0 a recent solution described in WO 89.057.48 proposes a single shaft mounted on a traction cradle connected to a harness. This cradle rests on the back of the horse by means of two cushions which bear on the superficial muscles at the junction of the back, of the withers, and of the shoulder. The shaft is articulated on the cradle about a vertical pivotal axis. This device, if it is suitable on flat terrain, is however not satisfactory because the pads bruise the horse, and on broken ground the cradle has a tendency to slide laterally on the back along sloping paths. Thus the tractive forces are badly distributed not only in the vertical plane but also in the horizontal plane. PA0 a saddle bow of a length between the pommel and the cantle of at least about 350 mm, prolonged forwardly on each side of the withers and comprising padding over all the surface that bears on the back of the horse, PA0 two pairs of lateral straps of adjustable length mounted in known manner on the flanks of the bow and connected to a belly band, PA0 a ball joint integrally affixed at the forward end of the pommel of the bow, projecting upwardly, PA0 and the forward end of the shaft comprises a cup, of a type known per se, of a shape corresponding to the spherical ball and such that the cup can incline in all directions on the sphere. PA0 the sphere is forwardly inclined along the longitudinal axis of the horse at an angle of about 7.degree. with respect to the vertical; PA0 the bow is a bow of the cavalry saddle type; PA0 the lateral forward strap comes into engagement on the bow at the most advanced point and the rear strap comes into engagement at the rear such that the resultant of the forces exerted on the sphere and applied to the bow will be parallel to the plane defined by the belly band; PA0 the belly band is of a minimum width of 70 mm and preferably 150 mm; PA0 moreover the device is completed by a hunting collar used as a breast collar, and by a crupper-loop.
Thus when the shaft is coupled to a collar which bears forwardly or in vertical alignment with the withers, the tractive forces can be great but impede the movements and wound the horse, and when a small harness saddle is maintained in a known manner, by straps forward of the withers, it does not permit resisting high tractive forces and the pivotal articulation gives rise to undesirable veering.